PERFORMANCE EVALUATION OF POLYMER MODIFIED AND UNMODIFIED SUPERPAVE MIXES

Abstract

The aims of this study were to evaluate the effects of aggregate gradation and polymer modification on rutting and fatigue resistance of Superpave mixes. Asphalt mixes were prepared using 3 different gradations (above, through, and below the restricted zone) and 3 PG 70-22 binders (unmodified, SBS and SBR modified), and were evaluated using a triaxial repeated load test, a static creep test, the Asphalt Pavement Analyzer test, and the flexural beam fatigue test. When aggregates meeting Superpave angularity requirements was used, the effects of gradation on the rut and fatigue resistance of Superpave mixes were relatively small. Even though binders used in this study had similar dynamic shear moduli, mixes containing polymer modified binders showed much lower resilient moduli than the unmodified mixes when measured in the indirect tensile and triaxial compressive modes. All lab test results indicated that the polymer modified mixes were markedly more rut resistant and fatigue resistant than the unmodified mixes with the same PG grading. Improvement in rut resistance due to polymer modification was shown to be most significant in the triaxial repeated load test, especially at a higher temperature. In summary, the Superpave mixes were highly rut resistant and effects of gradation variation on rut and fatigue resistance were small. The mixes with SBS and SBR modified binders were more rut and fatigue resistant than the unmodified mixtures. The triaxial repeated load test showed much more sensitivity to polymer modification than the uniaxial static creep test.